PRDX5 Regulates Mitochondrial Function and Nuclear Spreading in Myogenesis and Acts With PRDX3 to Delay Muscle Aging.

<p><b>BACKGROUND</b></p><p>Skeletal muscle aging is associated with oxidative stress and mitochondrial dysfunction. Peroxiredoxins (PRDXs), particularly PRDX3 and PRDX5, are antioxidant enzymes that are uniquely localized to mitochondria.

While PRDX3 has been reported to play a role in maintaining mitochondrial function in muscle, the specific function of PRDX5 in muscle remains unclear. This study investigated the role of PRDX5 in mitochondrial function, myonuclear distribution and muscle aging.</p><p><b>METHODS</b></p><p>Myoblasts were isolated from wild-type (WT), Prdx3 -/-, Prdx5 -/- and Prdx3 -/-; Prdx5 -/- mice crossed with mitochondria reporter (mt-GFP) mice.

Nuclear and mitochondrial positioning were evaluated using confocal and super-resolution lattice structured illumination microscopy (SIM). Mitochondrial function was assessed by Seahorse oxygen consumption rates (OCR) assays.

In vivo analyses included grip strength, treadmill performance and histological evaluation following venom-induced muscle injury.</p><p><b>RESULTS</b></p><p>During myogenesis, Prdx5 -/- and Prdx3 -/-; Prdx5 -/- myotubes exhibited impairments in nuclear spreading, characterized by clustered nuclei, unlike the even distribution observed in WT and Prdx3 -/- myotubes (44.4% and 44.9% vs. 17.1% and 21.9%, respectively; p < 0.001). Mitochondrial ATP production was significantly reduced in Prdx3 -/-, Prdx5 -/- and Prdx3 -/-; Prdx5 -/- myotubes (p < 0.05).

The expression of Rhot1 and Trak1, key regulators of mitochondrial transport, was significantly decreased in Prdx5 -/- and Prdx3 -/-; Prdx5 -/- myotubes (p < 0.01). Knockdown of Rhot1 or Trak1 in WT myotubes led to myonuclear clustering similar to that observed in Prdx5-deficient myotubes, supporting that PRDX5 facilitates mitochondrial transport and nuclear positioning, at least in part, through transcriptional regulation of genes including Rhot1 and Trak1.

In vivo, 48-week-old Prdx5 -/- mice exhibited mitochondrial dysfunction and myonuclear clustering in myofibers, with reduced treadmill performance (p < 0.05). Muscle regeneration was impaired in Prdx5 -/- mice, with decreased expression of regeneration and mitochondrial transport markers and increased nuclear clustering in regenerating myofibers (p < 0.05).

Prdx3 -/-; Prdx5 -/- double-knockout mice displayed accelerated muscle aging, including decreased muscle mass and strength, and elevated expression of E3 ligases Atrogin1 and MuRF1 as early as 10 weeks of age (p < 0.05). These mice also exhibited increased mitochondrial H 2O 2 production, which upregulated the expression of Atrogin1 and MuRF1 (p < 0.05).</p><p><b>CONCLUSIONS</b></p><p>Our findings reveal a previously unidentified role of PRDX5 in coordinating mitochondrial function and nuclear positioning during myogenesis and muscle regeneration.

The combined deficiency of PRDX3 and PRDX5 accelerates muscle aging by exacerbating oxidative stress and mitochondrial dysfunction, suggesting that enhancing their activity may be a promising therapeutic strategy to prevent sarcopenia and age-related muscle degeneration.</p>